Abstract: Geological storage of carbon dioxide is the key link of carbon dioxide capture, utilization and storage (CCUS) technology. Marine carbon dioxide geological storage is the process of injecting supercritical carbon dioxide captured by industrial carbon emission sources or oil and gas development into geological bodies, such as seabed salt water layers, abandoned or developing oil and gas reservoirs, to achieve long-term isolation from the atmosphere. Because it is far from human habitation and covered by sea water, it has the characteristics of "high safety and low environmental risk", the geological storage of Marine carbon dioxide has been highly valued by European and American countries and regions. Based on the analysis of the basic geological conditions of sedimentary basins in China Sea area, an innovative model volume method is used to evaluate the geological storage potential of carbon dioxide in brackish layers of sedimentary basins in China Sea area. The analysis shows that the sedimentary basins in the sea area of China have large Cenozoic thickness, good crustal stability, characteristics of middle and low geothermal field, multiple sets of carbon storage and capping combinations, more structural and stratigraphic traps, superior geological conditions for carbon dioxide storage, and great potential for salt water reservoir storage. This will provide a basis for the evaluation of marine carbon dioxide geological storage zones and the optimization of target areas, and has great significance for the path planning of carbon peaking carbon neutrality and the pre-study of offshore carbon dioxide geological storage demonstration projects in China's coastal provinces and cities.